Wing Tip Weight

[Tom Strom]

I am sure this has been covered somewhere before, but I can't find it.  I just finished a kit built Brodak Pathfinder.  I moved in December and lost my instruction book.  How much tip weight should I put in for initial test flights?  How do you know if you have too much or not enough?  Airplane weighs 48 oz. with LA .46 for power.  Also, where should it balance?  Line length?  It balances just behind the bottom spar, in the landing gear block area.  I made a set of lines that are 61', eye to eye.  I am not new to control line, just new to trying to make them fly proper, and present a decent flight pattern.  Any and all help is appreciated.

Tom

[Dick Pacini]

Call Brodak and they will be happy to furnish you with another instruction book.  There might be a slight charge, but I'm betting there won't be.  The CG should be on the plans.

If you don't have any luck getting a new book, send me a PM and I will photocopy mine and send it to you.  My kit isn't assembled yet and is buried under other kits in my workshop.

[Jack Mulinix]

 Hello Tom, I have a brodak pathfinder I finished last year. Flies great. LA 46, 12 1/4 x 3.75 apc, 1 1/2 oz tip weight, leadouts 3/4in back from CG, 60 ft eye to eye lines. weights 49 oz rtf.CG is at the spar. Hope that helps. Jack

[Mike Haverly]

Tom,
   Here is the information that will help you trim about any model.  http://www.aeromaniacs.com/Benchtrim.htm
Pete Peterson was involved with this designs development.  He says CG belong "just behind" the spar.  Tip weight should be enough to tip it over when balanced on the vertical fin and nose.  1 1/2 oz. sound like quite a lot but a little extra won't hurt to start.  I've seen you fly, and you are no beginner so tape the hinge lines and make sure the CG is correct.  12.25 x 3.75 APC is the correct prop.  We use that set up around these parts a lot.  10/22 Powermaster or 10/18 Wildcat fuel is the best.  The Wildcat is available in Tacoma and works best for me.  Drop by some time and go flying with me and Pete, we go to Auburn Airport a lot. 

[Derek Barry]

If the outboard wing is up when flying right side up and inverted there is not enough tip weight. If it flies down both ways or drops the tip when doing corners you have too much.

Leadouts will have to be adjusted when playing with tip weight. As you add tip weight you will have to move the leadouts forward and as you take weight away you will need to move them back. This is assuming that you are in the ballpark to begin with.

Derek

[Mike Haverly]

If the outboard wing is up when flying right side up and inverted there is not enough tip weight. If it flies down both ways or drops the tip when doing corners you have too much

Derek

I always try to get that condition before adjusting tip weight by checking for warps or necessary flap tweaks.  How many times have you seen models that are badly out of trim everywhere else because the pilot (usually inexperienced) tries to accomplish level flight by adjusting tip weight.  Hinging, roll and yaw are of course results of wrong tip weight one way or the other but *my* goal is always to get the same condition upright and inverted, without that you have nothing IMO.  Also, gap sealing is important to achieve equal rates of turn, again nothing gained otherwise.  Reference PW's trim chart.

[Derek Barry]

I always try to get that condition before adjusting tip weight by checking for warps or necessary flap tweaks.  How many times have you seen models that are badly out of trim everywhere else because the pilot (usually inexperienced) tries to accomplish level flight by adjusting tip weight.  Hinging, roll and yaw are of course results of wrong tip weight one way or the other but *my* goal is always to get the same condition upright and inverted, without that you have nothing IMO.  Also, gap sealing is important to achieve equal rates of turn, again nothing gained otherwise.  Reference PW's trim chart.

Very true but generally if the flaps need to be tweaked the wing will fly up one direction and down the other. Too much or too little tip weight will just compound that problem.

Derek

[Tom Strom]

Thanks all for the replies.  As usual, useful information.  Mike, if the wind and rain ever stop here, I will have to take you up on the offer.  Again, thanks to all who replied. 

Tom

[Garf]

I have a NoblARF that comes loose on insides above 45* but is tight on outsides above 45*. I think the flaps need to be tweaked.

[Bill Little]

I actually flew my Parrott P-47 at Huntersville with out tip weight.  Found out when I got home..........   (it does have some asymmetry and I used heavier wood on the outboard panel)

BIG Bear
RNMM/AMM

[Mike Haverly]

Two words. BENCH TRIM!

[Bill Little]

Two words. BENCH TRIM!

HI Mike,

It was bench trimmed....... about 10 years prior.   But I didn't go back and check after I stripped and refinished it............

BIG Bear
RNMM/AMM

[Bill Little]

My bench is level , is that the same thing.?? 

But is it FLAT?



Bill